Screening and comminuting device

ABSTRACT

A device for comminuting and screening solids in a stream of fluid material having a conical rotary screen on which cutters are mounted for coaction with stationary cutters and which is formed for circular elements of sequentially increasing diameter and spacing therebetween supported on an axle by precut ribs and on which cam locks hold cutting elements at preset angles to the direction of rotation, the screen being driven at its largest diameter be a flexible belt and supported at both ends in a flow directing enclosure for unitary installation in a flow channel.

United States Patent [1 1 Rudzinski [45] Ma 28, 1974 i 1 SCREENING ANDCOMMINUTING DEVICE Primary Examiner Roy Lake [76] Inventor: Stanley P.Rudzinski, l 156 S. Assismm ""P Jones Lombard Ave. Oak Park I. 60304Attorney, Agent, or F1rm-Jarrett Ross Clark [22] Filed: Feb. 5, 1973[57] ABSTRACT [2]] App! 329585 A device for comminuting and screeningsolids in a stream of fluid material having a conical rotary screen [52]U.S. CI. 210/174, 210/77 0" which Cutters are mounted for coactioh with[51 Int. Cl. C020 1/22 tionary cutters and which is formed f r ircul rele- [58] Field of Search r. 210/174, 152, 77, 79 menls of sequentiallyincreasing diameter and Spacing v therebetween supported on an axle byprecut ribs and [5 R m- Cited on which cam locks hold cutting elementsat preset angles to the direction of rotation, the screen being UNITEDSTATES PATENTS driven at its largestdiameter be a flexible belt and2,336,069 12 1943 Chase 210/174 Supported at both ends in a howdirecting enclosure for unitary installation in a flow channel.

' 18 Claims, 10 Drawing Figures PATENTEDIAYZWH amass? I am 1. 0f 3 I IJJl -f lllll thereof by large solid pieces.

1 SCREENING ANDCOMMINUTING DEVICE The present invention'relates to animproved device of the type described and claimed in my U. S. Pat. No.3,074,555, issued Jan. 22, 1963, for screening and comminuting solids ina stream of fluid material such as the solids occurring in the fluid insewage treatment plants and in drainage and other fluid treatmentsystems.

It is a general object of the present invention to provide an improvedrotor construction and support for screening and comminuting devices ofthe type having a rotating cutting and screening assembly. A relatedobject is to provide a more uniform distribution of solids to thecutting and screening elements and of fluid flow through the rotor.

A more detailed object of the invention is to provide an improved meansfor mounting individual cutters on the rotor to simplify adjustment andreplacement. It is also a purpose of the invention to mount the cuttersfor better cutting action and for minimizing jamming A further aim ofthe present invention is to provide an improved drive for the rotorwhich is more flexible in application and permits easier maintenance.

It is also an object of the invention to provide an improved method ofconstructing the rotor to increase stability of rotation and alignmentand to reduce the cost of manufacture.

The foregoing objects and others which will become apparent from thespecification are intended toprovide a device adapted for unitaryinstallation in fluid flow channels or conduits of various forms andconstruction and which is capable of efficient service and low costmaintenance under the adverse conditions of corrosion, widely varyinglevels of flow and diverse types of solids occurring in sewage treatmentand other fluid treatment systems.

The following is a detailed description of the preferred embodiment ofthe invention taken in connection with the accompanying drawings inwhich:

FIG. 1 is a perspective of a screening and comminuting device embodyingthe present invention and positioned in a portion of an exemplary fluidflowchannel;

FIG. 2 is a side elevation of the device of FIG. 1; FIG. 3 is a rearelevation of the device of FIG. 1; FIG. 4 is a side elevation of theradial support for the screening elements showing the method ofassembly;

FIG. Sis a front elevation of the structure of FIG. 4;

FIG. 6 is an exploded partial perspective ofa screening element with acutter and locking device;

FIG. 7 is a partial top view of a screening element with a cutter andlocking device assembled;

FIG. 8 is a side view of a locking element for the cutters;

FIG. 9 is a partial perspective of a stationary cutter bar, cutters andshield; and

FIG. 10 is a partial plan view of a modified cutter arrangement showingthe relation of the movable and stationary cutters.

Referring to the drawings in more detail, an improved comminuting andscreening apparatus 10 embodying the present invention is shown adaptedfor use in a rectangular liquid flow channel 11 which may carry sewageor other fluid having solids which must be comminuted or removed priorto treatment or discharge, As shown in FIG. 1, the apparatus comprises arotor 12, a support structure 13, a drive mechanism 14 and flowdirecting means. Carried by the rotor 12 and support structure 13 arecooperating movable and stationary cutting units l7, 18 for cutting andcomminuting solids contained in fluid flowing in the channel. In theassem- FIG. 1, the fluid flow i s [1311 left to right and forconvenience in describing the mechanism hereinafter,

the upstream or left end of the assembly will sometimes .be'referred toas the front and the downstream or right end will be referred to as therear of the assembly.

The apparatus of the present invention has a single driven part which isthe rotor 12. To provide a durable and solid mounting for the rotor,front and rear bearings or journals 19, 20 carry a rotor axle or shaft211. for rotation on an axis that is substantially parallel to thedirection of liquid or fluid flow. The support structure is formed by afore and aft base plate '22 extending for approximately the length ofthe rotor shaft 2], and in the form shown in the drawings for a squareor rectangular channel is a flat plate lying on the bottom wall of thechannel. Mounted on the front and rear portions of the base 22 andaligned with the midline of the base are front and rear vertical supportcolumns 24, 25. At the upper ends of the columns, flathorizontalsurfaces are formed by cross members or plates 26. To thesehorizontal surfaces are attached the bearings 19, 20 for re ceiving thefront and rear end portions of the rotor shaft 21. The bearings aresecured to the support columns by bolts 27 or other suitable fasteningmeans.

The rotor 12, as further described in US. Pat. No. 3,074,555, is ofconical shape but may be of other shapes formed as surfaces ofrevolution which increase in diameter from one end to the other. Inpracticing the present invention, the rotor 12 is constructed to increase its resistance to distortion from impact and uneven fluid flowand to reduce the cost of manufacture. For these purposes, the rotor issupported on the shaft 21 which extends from the front to the rear ofthe rotor with portions projecting from each end for insertion into thefront and rear bearings 19, 20. Assembled on the axle shaft 21 areradial ribs 29 pf generally triangul'ar shape and which on their outersloping edge have been formed with steps 30 for receiving circularscreening bars 31. As'best seen in FIGS. 4 and 5, the ribs 29 are spacedat equal angles around the circumference of the axle shaft 21, beingfour in number in the illustrative embodiment and spaced at ninetydegree angles around the shaft. Preferably, the ribs 29 are cut fromsteel plate, stacked together and machined as a unit to provide accuratealignment of the edge configurations. The ribs 29 are then placed intheir respective radial positions around the shaft 21 and are held inposition by appropriate fixtures 32. As shown in FIGS. 4 and 5, thefixtures 32 may be triangular plates which extend between adjacent ribs29 with their edges generally parallel to the sloping outer edges of theribs. Outwardly bent flanges 33 on the edges of the fixtures have holeswhich mate with holes in the ribs for receiving bolts 34 to hold theribs and fixtures in a fixed position about the axle shaft.

In the preferred form of the rotor, the circular screening bars 31 arealso cut or formed from flat steel plate as rings or annuli and are thenmachined on their inner diameter to match the radial spacing of therespective steps 30 on the ribs 29. For use with the form of ribs ofFIGS. 4 and 5, the inner circular face of the bars is formed as acylinder to mate with the corresponding axially directed steps 30 of theribs while the outer circular faces may be formed either as cylindricalsurfaces or as frusto-conical surfaces. An example of screen rings 31with cylindrical outer surfaces is shown in FIG. while frusto-conicalsurfaces are shown in FIGS. 2 and 6. At this time, slots 37 are cut inthe outer surfaces of the screen bars for receiving cutter bits 17 andsuitable holes 38 and counterbores 65' adjacent each slot are made forlocking means to hold the bits 17 in place as will be described in moredetail hereinafter. After machining, the screen bars 31 are placed ontheir respective steps. The ribs and screen bars are then fastened inplace, as by welding, with the inner edges of the ribs 29 fixed to theaxle shaft 21 and the bars 31 fixed to the stepped edges of the ribs.When the welding is completed the fixtures 32 are removed and the rotoris ready for insertion in the bearings 19, 20.

For the purpose of insuring accurate alignment of the bearings 19, andthe rotor 12 on the base support the bearings are placed on theprojecting end portions of of the rotorv shaft 21, and the bearings androtor are then placed on the receiving surfaces 26,0f the rotor supportcolumns 24, as a unit. Holes are now made in the mounting plates 26 onthe columns for receiving fasteners 27, orif desired, locating pins maybe used in addition to the fasteners 27. By this procedure, thecomminuting and screening apparatus can be delivered and installed as aunit without the necessity of adjusting the bearings at the time ofinstallation.

In another aspect of the present invention, an .improved drive mechanismhas been provided for driving the rotor. In the form shown in thedrawings, means are provided for directly driving the rotor 12 through adrive mechanism attached to the circumference of the rotor at itslargest diameter. In the preferred form, the drive mechanism includes asprocket ring 39 which together with seal and spacer rings 40, 41 arefastened by bolts 42 to the rear of the last screening bar 31 forunitary rotation. To obtain the desired driving forces, the outsidediameters of the sprocket ring 39 and largest screening bar 31 aresubstantially the same. Unobstructed outlet flow from the rotor isobtained since the inner diameters of the three rings 39, 40, 41 are thesame or slightly larger than the inner diameter of the last screeningbar 31. The seal ring 40, however, has a slightly larger outer diameterthan the other circular elements to permit its coaction with surroundingbaffle means while the outer diameter of the spacer ring 41 is somewhatsmaller to give clearance for the teeth on the sprocket ring 39. By theforegoing construction, the drive mechanism including the sprocket ring39 is shielded from the direct force and flow of the fluid. The drivesprocket ring 39 and its associated mounting rings 40, 41 may beattached to the rotor before the assembly fixtures 32 are removed fromthe ribs so that alignment is accurately maintained. As shown in FIG. 2of the drawings, the drive sprocket ring 39 is placed inboard, that is,in front, of the rear rotor support column 25 to further minimize anytendency for the rotor to be drawn out of alignment by driving forces orshocks from cutting hard materials.

Surrounding the drive sprocket ring 39 is a drive chain 44 which leadsupwardly to an overhead drive transmission 45 and source of power, suchas an electric motor 46. The output shaft of the transmission 45 carriesa sprocket gear'47 around which the upper portion of the chain 44 istrained'to complete the drive. To maintain tension on the chain 44', anidler sprocket 49 engages the outer side of the chain 44 at a pointbetween theringsprocket 39 and the sprocket gear 47 and above the top ofthe rotor 12 to keep'the sprocket 49 out of the flow of fluid. The idlersprocket 49 is journaled on a short arm 50 which is pivoted at its lowerend to a vertical rear baffle plate 60. A spiral spring, not shown,located around the pivotal mounting for the idler arm 50 presses theidler sprocket 49 against the chain 44 to take up any slack in the chainand provide ,the desired chain tension. The idler sprocket 49vis placedin the return flight of chain, that is, the portion of the chain that ismoving downwardly from the transmission sprocket gear to the ringsprocket. If it is desired to have the rotor direction reversible, twoidler sprockets, one on each flight of chain can be used to maintaintension in either direction of rotation. To protect the rotor and drivemechanism in case of shock or jamming of the rotor, it is desirable tolimit the maximum driving force by means of a preset overload clutch inthe transmission or an electrical overload cutout in the motor circuit.

With the present drive mechanism, great flexibility and protection ininstallation and use is achieved. The apparatus of the present inventionmay be easily adapted for many different mounting positions of the drivemotor 46 and transmission 45. The mounting illustrated in the drawingsis formed by a pair of vertical side supports or legs 51 extendingupwardlyfrom the bottom base plate 22 at the respective sides of theapparatus out. of the way of the stream of fluid. A cross plate 52 onthe top of the legs 51 forms a platform on which the motor 46 andtransmission 45 are mounted. It is apparent that depending on therequirements of a particular installation, the legs 51 may be madelonger or shorter to raise or lower the drive transmission 45 to theappropriate height without changing any other portion of the apparatusexcept for the use of a drive chain 44 of suitable length. The motor 46and transmission 45, if necessary, can also be mounted entirely separatefrom the remainder of the apparatus, such for example, as on the upperends of the channel side walls.

To direct the flow of fluid to and through the rotor screen anarrangement of baffles and shields surrounds the rotor assembly 12. Tothis end, provision is made for not only controlling fluid flow but alsofor providing ready access to the mechanism for maintenance andadjustment and for safety in the event of unexpected upstream pressureon the rotor screen. For this purpose, upright side walls 54, 55 arefixed to the longitudinal edges of the bottom base plate 22. They extendupwardly therefrom to above the seal ring 40 and rearwardly from forwardof the front rotor bearing 19 to at least the rear one of the rotorscreen bars 31 for channeling fluid flow along the sides of the rotor.The side walls 54, 55 may also provide added support for the drivemechanism by fastening the support legs 51 to the rear edges of thesidewalls. Preferrably at least one of the side walls 55- has aremovable upper portion which as shown in FIG. 1 is a sliding panel 56engaged at its front and rear ends by pairs of horizontally spaced apartvertical bars 57 forming vertical slideways. Additional flow control isprovided by front and rear transverse vertical baffle panels 59, 60which are attached at their bottom edges to the front and rear edges,re-

spectively, of the bottom base plate 22 and at their vertical edges tothe adjacent vertical end edges of the side walls 54, 55 and to thevertical slideway bars 57. The center portion of each end baffle has acircular opening 61, 62 which defines respective fluid inlet and outletopenings of a diameter corresponding to the largest diameter of therotor 12. The rear baffle panel 60 is positioned such that it is alignedwith the seal ring 40 on the rotor and forms a relatively close fittherewith to prevent or reduce flow around the outside of seal ring 40and hence to prevent or reduce the bypassing of fluid around the rotorscreen and cutters. interposed between the front and rear baffles 59, 60is a semicylindrical baffle 63 extending longitudinally of, and below,the rotor 12. The concave side of the baffle 63 faces upwardly enclosingthe lower portion of the rotor and has an inner diameter substantiallyequal to that of the flow openings 61, 62 in the end baffles. This foreand aft baffle 63 serves to smooth out the fluid flow and reduceturbulence which would otherwise exist in the lower part of the spaceenclosed by the baffles.

Enclosing thetop of the apparatus is a cover panel 65 which is fastenedto the front baffle plate 59 by hinges 66 at its front edge for upwardswinging movement of its rear portion. in the closed position, the edgesof the cover panel 65 rest on the top edges of the side and end panels.The cover panel serves both to protect the mechanism from solid objectswhich might be dropped on it and to prevent persons from contacting themoving rotor and being injured. In addition, it provides a safety escapefor fluid should an excessive pressure develop within the baffleenclosure. in such a case the rear portion of the cover panel 65willrise and permit excess fluid to spill over the rear baffle 60 to thedownstream side of the apparatus. The hinged cover panel 65 and theremovable side panel 56 also permit ready inspection and access to therotor and cutting mechanism for repair and adjustment.

It is a feature of the present invention that the baffle plates,particularly the front and rear plates 59, 60 can be shaped to fitvarious channel shapes without changing the basic rotor construction.Where a flow channel is unusually wide, two or more units may be placedside by side and appropriately shaped front and rear baffle plates tofit across the entire channel may be used. Separate flow openings wouldbe provided in the baffle plates for each of the rotors required tohandle the flow volume of the channel. The apparatus of the presentinvention may also be adapted for other shapes of channels thanrectangular. A V-shaped channel, for ex-. ample, would merely require amatching bottom support plate 22 and front and rear baffle plates 59, 60having V-shaped bottom edges. Similarly, the base plate 22 can be formedas a semi-cylinder for round bottomed channels and in appropriateinstances, the semi-cylindrical baffle plate 63 may become the baseplate Should a particular installation involve a tubular conduit.flanges can be provided at the front and rear ends of the apparatus forattachment to mating flanges on the conduit. ln this instance, the upperportion of the enclosure can also be semi-cylindrical to correspond tothe shape of the conduit.

As previously stated herein, provision is made in the annular screenbars 31 of the rotor for holding movable cutters which coact withcooperating stationary cutters 18. The movable cutters 17 for the rotorare rectangular bits of cutting material such as hardened steel and havea width toform a cutting edge which is substantially as long as thewidth of the screen bar. In accordance with an aspect of the invention,an improved locking means is provided for securely holding the cutterbits in the rotor but at the same time permitting ready release of thebits for reversing them to present a new cutting edge or forreplacement. To this end the screen bar 3i has an aperture 38 in itsouter surface adjacent to each cutter slot 37 as best seen in F E68. 6and 7. Surrounding the aperture 38 is a eounterbore 68 which has aportion of one side opening into the receiving slot 37. Received in theaperture 38 is a locking element or pin 69 which has a cylindrical shank70 for in sertion into the aperture 38 and an enlarged, flat head 71having a height equal to or slightly less than the depth of theeounterbore 68 so that the top surface of the head 71 is generally levelwith, or slightly below, the outer surface of the screen bar 31. Theperiphery of the head 71 is cam shaped, having a flat portion 72 thatextends approximately to the adjacent side edge of the bit receivingslot 37. The remaining periphery 73 of the head 71 gradually increasesfrom a radius equal to the distance of the flat portion 72 from theshank axis to a. radius greater than the distance of the shank axis tothe slot so that the edge of the head 71 at the larger radii overlapsthe adjacent edge of the receiving slot 37. Centrally of the head 71 isa slot or other means, such as polygonal opening '74 for receiving anAllen wrench, for manually rotating the lock pin 69 between release andlock positions. 0

Although the locking means of the invention is simple to manufacture, itsecurely holds the cutter bit and does not have the tendency to corrodeand freeze in place as happens with ordinary screw and nut fasteners.Any tendency of the locking element 69 to bind can be overcome byextending the shank receiving aperture 38 entirely through the screenbar 3i so that a rod or other suitably sized tool can be pushed againstthe bottom end of the shank 70 to force the locking element 69 axiallyout ofthe bar. In operation, the locking element 69 is first turned withits flat head portion 72 toward the cutter receiving slot 37 to giveclearance for insertion of the bit. The element isthen turned on itsaxis in the direction of the arrow in H6. 7 to engage the cam portion ofits head with the side of the bit. Further turning of the lockingelement in the same direction presents sections of the head havinggreater radii toward the cutter bit which moves the cam portion 73 overthe adjacent edge of the receiving slot 31 and firmly cams the bitagainst the opposite side of the receiving slot locking it in place. Thebit is released by simply returning the locking element to its originalposition with a fraction of a turn in the reverse direction. 7

Cooperating with the movable cutters E7 on the rotor are stationarycutters 18 supported on the base support structure 13 in fixed positionsrelative to the rotor cutters. As best shown in H6. l of the drawings, ahorizontal support shelf or ledge 77 is fixed to the solid lower portionof one of the side wall panels 55 for holding the stationary cutterbits. The shelf 77 is of triangular shape with an inner sloping edge orbar portion substantially parallel to, and spaced from, the outersurface of the rotor 12. The cutter support shelf is positionedgenerally at the vertical level of the rotor axis and the forwardenlarged section of the shelf is connected as by bolts or welding to thefront rotor support column 24 to provide lateral support for the column24 and to insure that accurate alignment is maintained even through thefront column 24 and the shelf 77 may in operation be struck by heavypieces of solid material carried by the fluid. If desired a similarsupport shelf or ledge may be provided on the second side of the rotorfor additional stationary cutters should it be desired to have periodicreversal of rotor rotation.

Considering the stationary cutter bits 18, two forms are illustrated inFIGS. 9 and 10, respectively. The form of bit 18A shown in FIG. 9 ispreferred for use with rotor screen bars 31 having beveled or taperedouter faces. The working edge of the cutter bit 18A is L-shaped toprovide a longer cutting edge 78 for coacting with the end cutting edgeof the rotor bits 17 and a shorter cutting edge 79 extending'radiallytoward the rotor for coacting with a portion of the side edge of therotor bits. By this configuration, the active cutting edge length isincreased and any material such as string which may encircle or bedraped around the rotor bits is cut. The opposite end of the stationarybit 18A has a simlarL shape so that the bit may be turned over to exposea second set of cutting edges if the original set requires replacement.in FIG. 10, stationary cutter bits 183 of similar shape are shown foruse with screen bars 36 having their outer surfaces parallel with theaxis of the rotor 12. The cutting edges differ only in that the secondset of edges has the foot of the L-shaped edge projecting from theopposite side of the bit 188 rather than from the same side as in theform of FIG. 9. The bits 188 of FIG. 10 are positioned on the stationarycutter shelf or bar with their longer and shorter edges, respectively,parallel and perpendicular to the axis of the rotor 12 to correspond tothe respective positions of the edges of the rotor cutters, rather thanangled with respect to the axis as in fIG. 9.

Means are also provided for positively positioning and protecting thestationary cutter bits 18. Preferrably the bits 18 are set on adownwardly offset ledge 80, the inner edge of which is located withrespect to the movable cutters so that it abuts the inactive edge of thestationary bit 18 to position it in operative relation with the movablebits 17. A bolt 82 through a central hole in the bit and received in athreaded hole in the support shelf 77 is provided for securing thestationary bits in place. Protecting the bits 18 and their fasteners isan inverted U-shaped shield 83 extending for the length of the supportshelf 77 and having a width sufficient to cover the bits except for theprotruding cutting edge portions. Lugs 84 on the back side of the shield83 are apertured to receive bolts 84 which are threaded into holes inthe upper surface of the support shelf 77 for fastening the shields inplace.

Additional protection for both the movable and the stationary bits isgiven by angling the cutter receiving slots 37 in the rotor screeningbars 31 with respect to the axis of the rotor and direction of movementfor the cutters 17. As shown in FIG. 7, the slots 37 and consequentlythe cutting edges of the bits 17 are angled such that the cutting cornerof the bit, the corner that mates with the junction of the radial andlongitudinal stationary cutting edges ofthe bits 18, leads slightly asthe cutting engagement is made. An angle A as shown in FIG. 7 of aroundfive to ten degrees is preferred. By so angling the cutting bits, hardsolids tend to be rejected or pushed out of contact with the cutters tominimize sudden shock on the cutters nd possible jamming of the rotor.

To further enhance the screening and cutting action of the rotor 12,means are provided for more uniform distribution of solid matter in thefluid flow and for cleaning the upstream facing portions of the supportstructure. To accomplish this, means are mounted on the front end of therotor axle 21 in the form of a distributing and cutting arm 87. In theillustrative embodiment this means comprises a rigid bar 87 extendingradially outwardly from the rotor axle 21. The inner end of the bar 87has an enlarged hub portion 88 which is apertured for the frontprojecting end portion of the axle shaft 21. The hub 88 may be split sothat it can be expanded to slide into place over the shaft. Fasteninglugs 90 are attached to each of the split hub sections for compressingthe hub opening by means of a bolt and nut to clamp the hub to theshaft. The arm 87 sweeps through the fluid entering the front baffleplate'59 to assist in breaking up any entangled masses of solids and inmoving solids generally around the surface of the rotor. The leadingedge of the distributing arm 87 is provided with a cutting blade 91 orset of cutting bits in the preferred form. The blade 91 extends alongthe length of the arm and projectsbeyond the rear side of the arm 87 forcoaction with a stationary cutting means mounted in fixed relation tothe path of revolution of the blade 91. As illustrated in FIG. 1, thestationary cutting'means is a blade 92 bolted to the top side of thesupport shelf 77 with a front cutting edge extending forwardly of theshelf into coacting position next to the path traversed by the cuttingedge of the blade 91 on the distributing arm 87. If desired a similarblade or set or cutting bitsmay be mounted on the forward edge of thefront rotor support column 24. These cutting edges assist in keeping theforward sections of the apparatus free'of stringy materials whichotherwise become entangled around the support column and cuttershelf.

In view of the foregoing, it will be seen that by the present inventionan improved comminuting and screening device is obtained. The improveddevice is intended to provide the screening action described in US. Pat.No. 3,074,555 in which the screen bars are spacedaxially from each otherand in which the outer diameter of each ring is greater than the innerdiameter of the next larger ring screening bar. The fluid must thus bendradially inwardly as it flows through the screen to enchance thescreening action. It is another feature of the present invention thatthe spacing between the screen bars will be varied axially from thesmall end to the large end of the rotor for more uniform and effectiveflow. As an example of such variation in spacing,.the screen bars at thesmall end of the rotor maybe spaced apart axially by an amountapproximately 50 greater than the spacing of the screen bars at thelarge end. The improved flow in one form of rotor may be obtained byspacing about one-third of the rotor length at the small end with aroundthreeeighths of an inch between screening bars and the remainingtwo-thirds of the rotor length at the large end of the rotor with aboutone-quarter of an inch betweenv bars.

I claim as my invention:

1. A device for screening and comminuting solids in a stream of fluidhaving rotor means including a series of axially spaced apart annularscreening bars of sequentially increasing diameter in the direction offluid flow, movable cutting means on said rotor and coacting stationarycutting means, wherein the improvement comprises in combination drivingmeans positioned out of the direct flow of fluid for rotating saidrotor, means for supporting said screening bars including an axle shaftand means extending outwardly from said shaft for positioning each ofsaid screening bars concentrically therewith, and means for supportingsaid shaft including a base member and support members extendingupwardly therefrom for engaging the front and rear portions of saidshaft for rotation thereof on an axis substantially parallel to thedirection of fluid flow.

2. The device of claim 1 in which said means extending outwardly fromsaid axle shaft include a plurality of ribs equally spaced around saidshaft, each of said ribs having an edge portion extending axially alongsaid sbaft a distance equal to the axial length of said series of barsand having an outer sloping edge portion for receiving and positioningsaid series .of bars.

3. The device of claim 1 in which said driving means includes an annulardriving member having a diameter substantially equal to the diameter ofthe largest of said screening bars and drivingly affixed to the rearthereof, power means positioned above said rotor and above the level offluid flow, and flexible belt means trained around said driving memberfor interconnecting said power means and said driving member.

4. The device of claim 3 in which said annular driving member is a ringsprocket and said flexible belt means is a power transmitting chain.

5. The device of claim 3 in which fluid baffle means surrounds saidrotor adjacent the largest of said screen bars and forwardly of saidannular driving member for minimizing flow bypassing said rotor andshielding said drive means from direct flow of fluid.

6. The device of claim 5 in which upright side panels extend forwardlyfrom the side portions of said fluid baffle means to the front of saidrotor and a second baffle means having an opening for fluid flow extendstransversely between said side panels at their forward portions fordirecting fluid to said rotor.

7. The device of claim 1 in which said shaft supporting means includesrigid means extending laterally from an upper portion of the front oneof said upwardly extending support members and connected to said basemember for resisting sideward movement of said rotor shaft.

8. The device of claim 7 in which said rigid means also extendsrearwardly along the outer face of said rotor and means for mountingsaid stationary cutting means thereon.

9. The device of claim 1 in which a front projecting portion of saidaxle shaft has a radially extending arm attached thereto for rotationwith said rotor for distributing solids in said fluid to said screeningbars.

10. The device of claim 9 in which said arm has movable cutting meansand a forward facing portion of said shaft support means has coactingstationary cutting means for removing solids carried by the fluidagainst said forward facing portion.

11. A device for screening and comminuting solids in a stream of fluidhaving rotor means including a series of axially spaced apart annularscreening bars of sequentially increasing diameter. movable cuttingmeans on said rotor and coacting stationary cutting means, wherein theimprovement comprises in combination an axle shaft extending lengthwiseof said series of annular screening bars and concentric therewith, aplurality of ribs equally spaced around said shaft and extendingradially therefrom, said ribs each having a series of stepped recessesin their outer edge portions, said stepped recesses being atsequentially increasing distances from the axis of said shaftcorresponding to the sequentially increasing inner diameters of saidscreening bars for receiving and holding said series of screening barson said ribs in axially spaced apart relation, said ribs being affixedto said shaft at least at points substantially perpendicular withrespect to the end portions of said series of screening bars, andupright sup- -port means having bearings means at the upper portionsthereof for receiving projecting end portions of said shaft for rotationabout the axis thereof.

12. The device of claim ill in which the spacing between annularscreening bars of large diameter is less than the spacing betweenannular screening bars of small diameter.

13. The device of claim ill in which the spacing be tween adjacentscreening bars increases as the diameters of the bars decrease.

14. A device for screening and comminuting solids in a stream of fluidhaving rotor means including a series of axially spaced apart annularscreening bars, movable cutting means on said rotor and coactingstationary cutting means wherein the improvement comprises incombination flat sided movable cutter bits having at least one cuttingedge, said screening bars defining transverse slots in their outersurfaces having a width substantially equal to the thickness of saidbits and having a depth less than the length of said bits for receivingsaid bits with the'cutting edge thereof projecting be yond the outersurface of said bars, the outer surface of said screening bars having anaperture therein adjacent each of said slots, and a locking elementhaving a cylindrical shank portion received in said aperture and a camshaped head portion the radius of which increases from an amount lessthan the distance of the axis of the shank portion from the adjacentside of a cutter bit in said slot to an amount greater than said distance for releasably locking said cutter bits in said slots uponrotation of said locking element about said shank axis to force saidhead portion into clamping egagement with said cutter bits.

15. The device of claim M in which the outer surface of said screeningbars also has a recess surrounding said aperture, said recess having adepth at least as great as the thickness of said locking element headportion and opening into said bit receiving slot, said head portionbeing received in said recess.

' 16. The device of claim 14 in which said cutter bit receiving slotsare angled with respect to the central axis of said screening bars suchthat one corner of the cutting edge of said cutter bit engages thecoacting stationary cutter in advance of the remainder of the saidcutting edge.

17. The method of making a rotor for use in screening and comminutingdevices of the type having a rotor means including a series of axiallyspaced apart annular screening bars of sequentially increasing diameterand movable cutter means on said rotor, comprising in combinationcutting a series of annular bars of sequentially increasing diametersfrom metal plate material, machining the inner diameters of said barsparallel with the axis thereof and machining the outer diameters suchthat the outer diameter of one bar is larger than the inner diameter ofthe next larger bar, cutting a plurality of triangular ribs from metalplate material,

the shaft and the bars to the said ribs, and removing the fixtureelements thereafter.

18. The method of claim 17 in which the step of machining the annularscreening bars includes machining transverse slots in the outer surfacesof the bars for receiving said movable cutter means before mounting thebars on the steps of the ribs.

1. A device for screening and comminuting solids in a stream of fluidhaving rotor means including a series of axially spaced apart annularscreening bars of sequentially increasing diameter in the direction offluid flow, movable cutting means on said rotor and coacting stationarycutting means, wherein the improvement comprises in combination drivingmeans positioned out of the direct flow of fluid for rotating saidrotor, means for supporting said screening bars including an axle shaftand means extending outwardly from said shaft for positioning each ofsaid screening bars concentrically therewith, and means for supportingsaid shaft including a base member and support members extendingupwardly therefrom for engaging the front and rear portions of saidshaft for rotation thereof on an axis substantially parallel to thedirection of fluid flow.
 2. The device of claim 1 in which said meansextending outwardly from said axle shaft include a plurality of ribsequally spaced around said shaft, each of said ribs having an edgeportion extending axially along said sbaft a distance equal to the axiallength of said series of bars and having an outer sloping edge portionfor receiving and positioning said series of bars.
 3. The device ofclaim 1 in which said driving means includes an annular driving memberhaving a diameter substantially equal to the diameter of the largest ofsaid screening bars and drivingly affixed to the rear thereof, powermeans positioned above said rotor and above the level of fluid flow, andflexible belt means trained around said driving member forinterconnecting said power means and said driving member.
 4. The deviceof claim 3 in which said annular driving member is a ring sprocket andsaid flexible belt means is a power transmitting chain.
 5. The device ofclaim 3 in which fluid baffle means surrounds said rotor adjacent thelargest of said screen bars and forwardly of said annular driving memberfor minimizing flow bypassing said rotor and shielding said drive meansfrom direct flow of fluid.
 6. The device of claim 5 in which uprightside panels extend forwardly from the side portions of said fluid bafflemeans to the front of said rotor and a second baffle means having anopening for fluid flow extends transversely between said side panels attheir forward portions for directing fluid to said rotor.
 7. The deviceof claim 1 in which said shaft supporting means includes rigid meansextending laterally from an upper portion of the front one of saidupwardly extending support members and connected to said base member forresisting sideward movement of said rotor shaft.
 8. The device of claim7 in which said rigid means also extends rearwardly along the outer faceof said rotor and means for mounting said stationary cutting meansthereon.
 9. The device of clAim 1 in which a front projecting portion ofsaid axle shaft has a radially extending arm attached thereto forrotation with said rotor for distributing solids in said fluid to saidscreening bars.
 10. The device of claim 9 in which said arm has movablecutting means and a forward facing portion of said shaft support meanshas coacting stationary cutting means for removing solids carried by thefluid against said forward facing portion.
 11. A device for screeningand comminuting solids in a stream of fluid having rotor means includinga series of axially spaced apart annular screening bars of sequentiallyincreasing diameter, movable cutting means on said rotor and coactingstationary cutting means, wherein the improvement comprises incombination an axle shaft extending lengthwise of said series of annularscreening bars and concentric therewith, a plurality of ribs equallyspaced around said shaft and extending radially therefrom, said ribseach having a series of stepped recesses in their outer edge portions,said stepped recesses being at sequentially increasing distances fromthe axis of said shaft corresponding to the sequentially increasinginner diameters of said screening bars for receiving and holding saidseries of screening bars on said ribs in axially spaced apart relation,said ribs being affixed to said shaft at least at points substantiallyperpendicular with respect to the end portions of said series ofscreening bars, and upright support means having bearings means at theupper portions thereof for receiving projecting end portions of saidshaft for rotation about the axis thereof.
 12. The device of claim 11 inwhich the spacing between annular screening bars of large diameter isless than the spacing between annular screening bars of small diameter.13. The device of claim 11 in which the spacing between adjacentscreening bars increases as the diameters of the bars decrease.
 14. Adevice for screening and comminuting solids in a stream of fluid havingrotor means including a series of axially spaced apart annular screeningbars, movable cutting means on said rotor and coacting stationarycutting means wherein the improvement comprises in combination flatsided movable cutter bits having at least one cutting edge, saidscreening bars defining transverse slots in their outer surfaces havinga width substantially equal to the thickness of said bits and having adepth less than the length of said bits for receiving said bits with thecutting edge thereof projecting beyond the outer surface of said bars,the outer surface of said screening bars having an aperture thereinadjacent each of said slots, and a locking element having a cylindricalshank portion received in said aperture and a cam shaped head portionthe radius of which increases from an amount less than the distance ofthe axis of the shank portion from the adjacent side of a cutter bit insaid slot to an amount greater than said distance for releasably lockingsaid cutter bits in said slots upon rotation of said locking elementabout said shank axis to force said head portion into clamping egagementwith said cutter bits.
 15. The device of claim 14 in which the outersurface of said screening bars also has a recess surrounding saidaperture, said recess having a depth at least as great as the thicknessof said locking element head portion and opening into said bit receivingslot, said head portion being received in said recess.
 16. The device ofclaim 14 in which said cutter bit receiving slots are angled withrespect to the central axis of said screening bars such that one cornerof the cutting edge of said cutter bit engages the coacting stationarycutter in advance of the remainder of the said cutting edge.
 17. Themethod of making a rotor for use in screening and comminuting devices ofthe type having a rotor means including a series of axially spaced apartannular screening bars of sequentially increasing diameter and movablecutter means on said rotor, comprising in coMbination cutting a seriesof annular bars of sequentially increasing diameters from metal platematerial, machining the inner diameters of said bars parallel with theaxis thereof and machining the outer diameters such that the outerdiameter of one bar is larger than the inner diameter of the next largerbar, cutting a plurality of triangular ribs from metal plate material,stacking and machining said ribs in unison to form a straight side onsaid ribs having a length at least as great as the axial length of saidseries of screening bars and a sloping side having a series of steps forreceiving said series of screening bars, equally spacing said ribsaround a cylindrical axle shaft, removably fastening like fixtureelements between adjacent ribs for maintaining said spacing, mountingsaid series of bars on said series of steps, permanently fastening saidribs to the shaft and the bars to the said ribs, and removing thefixture elements thereafter.
 18. The method of claim 17 in wbich thestep of machining the annular screening bars includes machiningtransverse slots in the outer surfaces of the bars for receiving saidmovable cutter means before mounting the bars on the steps of the ribs.